A commonly used temperature measuring instrument consists of a thermocouple and a meter. As is well known, a thermocouple includes two elongated electrical conductors of dissimilar materials, which are joined at their ends to form two junctions. Because of the dissimilarity of the materials, EMFs are generated at the junctions, and the EMFs are functions of temperature. If one junction is hotter than the other, the EMF at the hot junction will be greater than the EMF at the cold junction. The resultant EMF will cause current flow in the conductors, and the meter can be designed to measure the current flow or the resultant EMF. The current and the resultant EMF are, of course, functions of the difference in temperatures between the hot junction and the cold junction.
While thermocouples work well in principle and in many applications, difficulties are encountered in many temperature measuring requirements. For example, in an instance where it is necessary accurately to measure the temperature of a heated metal member, the hot junction is normally pressed against the the member to raise the temperature of the hot junction up to that of the member to be measured. However, it is often difficult to make the hot junction exactly equal in temperature to that of the member. As another example, it is frequently necessary to measure the temperature of a liquid held in a container. It would be possible to submerge the thermocouple hot junction in the liquid, but this frequently is not desirable.
It is a general object of the present invention to provide an improved thermocouple-type temperature measuring instrument, and a method of measuring temperature, which overcome the disadvantages of the prior art.